diff --git a/lib/SimpleSAML/Utilities.php b/lib/SimpleSAML/Utilities.php
index 27b4da60057dbab50f40c4d86bf28744c6e99886..5dfd4d05172a01b1ac054cc51afb73a8fc94caaa 100644
--- a/lib/SimpleSAML/Utilities.php
+++ b/lib/SimpleSAML/Utilities.php
@@ -184,7 +184,7 @@ class SimpleSAML_Utilities {
 		}
 
 		$query = array_merge($oldQuery, $parameter);
-		$url .= http_build_query($query);
+		$url .= http_build_query($query, '', '&');
 
 		return $url;
 	}